One for the Brains Trust: Fuel Delivery & Fuel Pump Relay

[mattross]

Basis: Fuel Pump relay getting hot and lots of clicking - powered on too much.

OK, this is my guess - this hopefully some of the experts here can shed some light on this.

The Accelerator cable is attached to the throttle position sensor (TPS). When accel pedal is pressed the TPS picks it up and sends a signal to the ECU which uses this to power the Fuel pump relay, which powers the fuel pump. The issue i see is their is no fuel pressure feedback. Effectively the fuel can just be pumped around in circles (from tank to fuel rail thru the fuel pressure regulator back to the tank) as their should be a fuel pressure switch off mechanism for the fuel pump relay.

Is this correct or am i way off?

If correct, the fuel pump relay getting hot must mean that either the TPS is faulty or faulty signal from the ECU Or the fuel pressure regulator faulty?

[h100vw]

Basis: Fuel Pump relay getting hot and lots of clicking - powered on too much.

OK, this is my guess - this hopefully some of the experts here can shed some light on this.

The Accelerator cable is attached to the throttle position sensor (TPS). When accel pedal is pressed the TPS picks it up and sends a signal to the ECU which uses this to power the Fuel pump relay, which powers the fuel pump. The issue i see is their is no fuel pressure feedback. Effectively the fuel can just be pumped around in circles (from tank to fuel rail thru the fuel pressure regulator back to the tank) as their should be a fuel pressure switch off mechanism for the fuel pump relay.

Is this correct or am i way off?

If correct, the fuel pump relay getting hot must mean that either the TPS is faulty or faulty signal from the ECU Or the fuel pressure regulator faulty?

This bit > Is this correct or am i way off?

The fuel pump runs continuously. The crank position sensor is the trigger for sparks and fuel from the ECU.

The fuel is delivered to the rail and the excess fuel not injected, returns to the tank.

Gavin

[Jmac]

Fuel pump relay getting hot, what pointed you to check such?? it will get hot in normal operation anyway, there is hot and HOT. Whats it doing??? simple way to check a pump is to check how many amps its drawing. You should feel a MK5 terminal 30 and 15 relay, you could fry an egg on it in normal operation. So back to the top why you checking it????

[mattross]

Jmac, i had the air vents on feet and could feel a bit of heat every so often, so decided to check it out thinking the heater core box flaps may have gone. The Fuel pump relay was very hot, barely touchable - been driving for approx 1 hour solid. As a relay is just a switch, i dont understand why its getting hot. It must either be
1. faulty
2. drawing too much current for it (wire/components undersized),
3. is constantly switching on and off
to be getting hot.